Wireless local area networks (WLANs) use infrared (IR) or radio frequency (RF) communications channels to communicate between portable or mobile computer terminals and stationary access points or base stations. These access points are connected by wired or wireless communication channels to a network infrastructure which connects groups of access points together to form a local area network (LAN), which can include one or more host computers. In turn, the LAN can be connected to another larger network such as the Internet and the World Wide Web (Web). Several protocols, including the IEEE 802.11 standard, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications” have been designed to standardize WLAN communications. Such standardization is useful for optimizing user requirements, including spatial layout, response time, loading and throughput requirements of the network.
“Roaming” terminals are mobile units that can associate with any access point (AP) associated with a WLAN and seamlessly move from AP to AP. Each roaming terminal analyzes received signals from access points in its vicinity and associates with a single access point. Communication with an access point connects a terminal with the LAN and therefore with external networks such as the Internet. The region around an access point can be referred to as a “cell”. Roaming terminals can move from cell to cell and remain connected to the LAN and any other network to which the LAN has connected.
The IEEE 802.11 standard is one protocol used for WLAN communications. Typically, a mobile unit must be configured by hand by the manual entry of network and user parameters in order to be able to communicate with an access point. Once configured, each unit must be reconfigured if it is to communicate with another WLAN. Furthermore, each access point is associated with a finite number of frequency channels. Often, there can be several unrelated WLANs in a dense area such as an office building. These unrelated WLANs, or other RF communication systems, may use the same frequencies. Therefore it is possible for a mobile unit associated with one WLAN to pick up a communications interference with an unrelated WLAN. This situation is not desirable. Therefore, even if a roaming unit is to have the broadest possible communication coverage with an associated WLAN, unauthorized users from unrelated WLANs can possibly breach the communication link.
However, many users of roaming terminals expect to connect to multiple unrelated WLANs that do not create a security breach. For example, a company may have multiple offices around the world with a WLAN in every office. In such a situation, an employee of the company may want to use one roaming unit in several of the offices. The ability to connect to several unrelated WLANs requires a different configuration. However, it is burdensome to have to reconfigure the terminal each time the user desires to use the terminal with a different WLAN. Furthermore, if there are several roaming terminals for the several WLANs, attended installation of a new configuration is required for each of the terminals.